A trial comparing 2 different ways of doing a colonoscopy to screen for bowel cancer (CONSCOP)

Cancer type:

Bowel (colorectal) cancer

Colon cancer

Status:

Results

Phase:

Other

This trial looked at a way of doing a colonoscopy that involves spraying a blue dye throughout the large bowel. This is called contrast enhanced colonoscopy or chromocolonoscopy.

Everyone that took part had already given a poo (stool) sample as part of the NHS Bowel Cancer Screening Programme in Wales.

The bowel cancer screening programme aims to detect bowel cancer when it is at an early stage and treatment is more likely to work. It can also reduce the risk of bowel cancer developing in the first place by finding and removing small growths called polyps. If polyps aren’t removed, they may develop into cancer.

Cancer Research UK supported this trial.

More about this trial

This study started in 2014 and researchers looked at these results in 2018.

At the time this study was done, the NHS Bowel Cancer Screening Programme in Wales used a test called faecal occult blood (FOB) test to look for hidden traces of blood in poo samples. Hidden traces of blood can be a sign of bowel cancer.

You have a test called colonoscopy if the FOB test shows blood in your poo. A doctor or specialist nurse uses a small camera on the end of a thin, flexible tube to look inside your bowel. If they see polyps during the colonoscopy, they can remove them.

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But some people develop bowel cancer despite having a colonoscopy as part of the screening programme. These cancers are usually in the upper part of the large bowel, on the right hand side. They are sometimes caused by a type of polyp called serrated polyp. Serrated polyps are often flat and difficult to see during a colonoscopy.

Doctors wanted to see if spraying a blue dye throughout the upper part of the large bowel helps to find more serrated polyps. This is called a contrast enhanced colonoscopy or chromocolonoscopy.

The main aim of this trial was to find out whether a contrast enhanced colonoscopy is safe and can be used in the screening programme. If successful, then doctors want to do a larger trial to see if the contrast enhanced colonoscopy finds more people with serrated polyps that are close to become cancer.

Summary of results

The trial team concluded that a contrast enhanced colonoscopy helps doctors find and remove more serrated polyps. But doctors still need to find out if removing more serrated polyps during screening reduces the number of people who develop bowel cancer.

903 people were invited to take part in this feasibility study. Everyone had already given a poo sample (FOB test) as part of the Bowel Cancer Screening Programme in Wales. And the test showed hidden traces of blood in the poo.

Of the 903 people invited to take part, 741 agreed to join this trial. Everyone was put into 1 of the following groups at random:

381 people joined the contrast enhanced colonoscopy group
360 people joined the normal colonoscopy (standard test) group

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Number of polyps found

The trial team looked at the number of polyps found during the colonoscopies in both groups. There were:

903 polyps found in the contrast enhanced colonoscopy group
570 polyps found in the standard colonoscopy group

Doctors also wanted to look at the number of people with serrated polyps in both groups. Doctors found that:

45 out of the 381 people (almost 12%) who joined the contrast enhanced colonoscopy group had serrated polyps
23 out of the 360 people (about 6%) who joined the standard colonoscopy group had serrated polyps

Side effects

Researchers looked at the number of serious side effects that people in both groups had. There were 2 serious side effects in the standard colonoscopy group and 4 serious side effects in the contrast enhanced colonoscopy group.

The side effects were:

5 people had bleeding from the bowel
1 person had anxiety and a very fast breathing (hyperventilation)

More people in the contrast enhanced colonoscopy group had bleeding from the bowel than people in the standard colonoscopy group.

Doctors also found that there were no allergic reactions to the blue dye used in the contrast enhanced colonoscopy group.

What else did they find?

The research doctors also found that the average length of time it took to do the contrast enhanced colonoscopy was longer than the standard colonoscopy. It took:

around 37 minutes to do a contrast enhanced colonoscopy
around 31 minutes to do a standard colonoscopy

What did they conclude?

The researchers concluded that the contrast enhanced colonoscopy can be used since it does not take too much longer than a standard colonoscopy.

There weren’t many side effects, so doctors think that the contrast enhanced colonoscopy is a safe test.

Researchers hope to do a larger trial in the future. They want to find out whether or not the contrast enhanced colonoscopy finds more people with serrated polyps that are close to become cancer.

We have based this summary on information from the research team. As far as we are aware, the information they sent us has not been reviewed independently (peer reviewed) or published in a medical journal yet. The figures we quote above were provided by the research team. We have not analysed the data ourselves.